Mirrors are commonly used while bathing or showering to aid in personal grooming tasks. In a high humidity environment such as a bathroom, water vapor will often condense on a mirror surface causing the mirror to fog. It is therefore desirable to employ mirrors that can remain fog-free in a humid environment.
A method commonly used to prevent a mirror from fogging is to keep the temperature of the mirror higher than that of the dew point (i.e., the temperature at which water vapor in the ambient air will condense on a surface). The mirror temperature can be maintained above the dew point by employing a heating element for heating the mirror. Such heating elements are typically connected to an electrical source. Exemplary mirrors with heating elements are disclosed in U.S. Pat. No. 4,060,712 to Chang, U.S. Pat. No. 5,731,569 to Crescenzo, U.S. Pat. No. 6,420,682 to Sellgren et al., U.S. Pat. No. 6,796,665 to Pillinger, and U.S. Pat. No. 7,131,739 to Sellgren et al. Such mirrors can be difficult to install, because they require a connection to an electrical source. Furthermore, employing an electrical device in a moist environment can prove hazardous.
Mirrors can also be heated with hot water. Typically, hot water is drawn from a bathroom plumbing system and passes behind the mirror so that the mirror remains heated. Exemplary mirrors heated with hot water are disclosed in U.S. Pat. No. 4,832,475 to Daniels and in U.S. Pat. No. 5,313,316 to Davidge. Mirrors heated with water can be difficult to install and risk spraying or leaking water.
Other publications disclose more technical efforts used to prevent mirrors from fogging in the presence of steam. For example, WIPO International Publication No. WO 01/73483 to Casebier discloses generating static electricity on the surface of a mirror in order to repel water vapor and prevent the mirror from fogging.
U.S. Pat. No. 6,443,578 to Finnigan discloses using a fog free mirror employing coatings that prevent condensation on the surface of the mirror. Over time the performance of such coatings degrades, which, inter alia, may lead to a poor image quality.
Accordingly, it would be desirable to have a mirror that resists the formation of fog, is simple to install, and that does not degrade over time. It would also be desirable to have a mirror that requires less frequent cleaning than conventional shower mirrors.